1. Technical Field
The present invention relates to a television with a built-in DVD device in which a cabinet is formed by an insulating material, and more particularly to a television with a built-in DVD device in which a DVD device and a filter substrate connecting the DVD device to a television circuit substrate are covered with a shielding case.
2. Related Art
A DVD reproducing device radiates noise with a very large level due to an influence of processing of a digital image signal acting as animation. Because of this, a level of high-frequency noise radiated to the outside of a cabinet has been reduced by using a metal in the cabinet (called a first conventional art).
Also, in order to avoid complication of workability, a lead wire having a connector connected to a television circuit substrate has been used in a path for connecting the television circuit substrate to a filter inserted into a path for connecting the DVD reproducing device to the television circuit substrate for performing processing of an analog image signal (called a second conventional art).
Also, in a television with a built-in CD reproducing device, a conventional art for reducing noise occurring from the CD reproducing device has been proposed as the Unexamined Japanese Patent Application Publication No. Hei8-307783. That is, in this art, an operation of the CD reproducing device is stopped when a CD has not been inserted into the CD reproducing device. Also, when a CD has been inserted into the CD reproducing device, only a clock generating part of a voice system or a clock generating part of a video system is operated according to a kind of the inserted CD. Therefore, a level of radiation acting as interference is reduced (called a third conventional art)
[Problems to be Solved]
However, in the case of attempting to build the DVD reproducing device into a television, the following problems have been caused when the first conventional art is used. That is, when the DVD reproducing device and the television are integrated and a cabinet is formed of metal, a shape of the cabinet is large, so that a device becomes heavy. Also, a price of the cabinet increases.
And, an effect obtained by forming the cabinet of metal results in attenuation of unnecessary radiation to the cabinet outside. Because of this, the following problems cannot be solved.
That is, a television circuit for processing a signal of television becomes a circuit for processing a signal of an analog system. On the other hand, the DVD reproducing device becomes a device for obtaining an analog image signal finally by performing digital signal processing of a digital image signal recorded on an optical disk and a D/A conversion. And, a clock frequency becomes a very high frequency. Because of this, a level of high-frequency noise radiated from the DVD reproducing device is very large. Therefore, when both of a television circuit substrate and the DVD reproducing device are provided inside one cabinet, the noise radiated from the DVD reproducing device enters the television circuit substrate. As a result of that, a situation in which the noise mixes into a screen or a voice of the television has been caused.
Also, the following problems have been caused when the second conventional art is used. That is, it is necessary to have a margin of length in a lead wire for forming a path from a filter to the television circuit substrate, so that a bend occurs in the lead wire after the connection. Also, a shape of this bend varies largely every device. On the other hand, a level of high-frequency noise radiated from the lead wire becomes large as the lead wire becomes long. Also, the level varies largely depending on a bend condition of the lead wire. As a result of that, a level of the high-frequency noise radiated to the cabinet outside or a level of the high-frequency noise entering the television circuit substrate is large and the level varies largely every device.
Also, in the DVD reproducing device, a voice is reproduced simultaneously when an image is reproduced. Because of this, as in the third conventional art, a configuration in which only one generating part of a clock generating part of a video system and a clock generating part of a voice system is operated cannot be applied. That is, when the DVD reproducing device and the television are integrated, the third conventional art becomes an art difficult to apply.